Method for determining whether to allow flying thickness change, method for flying thickness change, device for determining whether to allow flying thickness change, and program for determining whether to allow flying thickness change

Abstract

To provide a method for determining whether to allow proper flying thickness change, a device for determining whether to allow flying thickness change and a program for determining whether to allow flying thickness change, which can accurately predict tension fluctuation during flying thickness change, even in a condition in which a material to be milled in which a preceding material and a succeeding material combined with each other have been actually operated less frequently in the past.SOLUTION: A method for determining whether to allow flying thickness change, which determines whether to allow flying thickness change when a tandem mill continuously mills a material to be milled in which a preceding material is joined to a succeeding material through a joint part, includes: a set value obtaining step of obtaining set values of a roll gap and a roll circumferential velocity at a milling stand with respect to the preceding material, before starting to change the set values of the roll gap and the roll circumferential velocity on at least one milling stand of the tandem mill; a tension fluctuation calculating step of calculating tension fluctuation when the joint part passes on the milling stand while maintaining the set values of the roll gap and the roll circumferential velocity with respect to the preceding material; and a determining step of determining whether to allow flying thickness change on the basis of the tension fluctuation calculated in the tension fluctuation calculating step.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a method for determining whether or not a thickness can be changed while on the move, a method for changing the thickness while on the move, an apparatus for determining whether or not a thickness can be changed while on the move, and a program for determining whether or not a thickness can be changed while on the move. [Background technology]

[0002] In the cold rolling process, a preceding material to be rolled (hereinafter referred to as "preceding material") and a succeeding material to be rolled (hereinafter referred to as "successive material") are joined (typically by welding) at the entry side of a tandem rolling mill, and the preceding and succeeding materials are cold rolled in the tandem rolling mill as a continuous metal strip. Then, at the exit side of the tandem rolling mill, the metal strip that has been cold rolled is cut at the position of the product unit, and the cut metal strip is sequentially wound up by a tension reel. When cold rolling the metal strip, if any of the hardness, base thickness, and finish thickness is different between the preceding and succeeding materials, "flying thickness change" is performed. "Flying thickness change" refers to a process of changing the rolling conditions before and after the joining part (also called the joining point) during continuous rolling in order to improve the yield without stopping the line.

[0003] If the rolling conditions change significantly before and after the joint when changing the thickness while running, the tension fluctuation amount increases when the joint passes through each rolling stand, and the metal strip may break or be squeezed. If the metal strip breaks or is squeezed, the operating efficiency of the tandem rolling mill decreases. Therefore, a technology has been proposed in which the tension fluctuation amount when the joint passes through each rolling stand of the tandem rolling mill is predicted, and if the predicted tension fluctuation amount is large, the operating conditions of the tandem rolling mill are changed. Specifically, Patent Document 1 describes a method of optimizing the running thickness change time so that the predicted tension fluctuation amount falls within an allowable range by providing a prediction means for predicting the tension fluctuation amount that occurs when changing the thickness while running. In the method described in Patent Document 1, the prediction means uses a tension generation model having a first-order lag characteristic and a correction term that has learned the actual tension fluctuation amount. Patent Document 1 also describes that the prediction means can be applied with a prediction means learned by a neural network that uses the actual value of the tension fluctuation amount as teacher data.

[0004] In addition, Patent Document 2 describes a method for predicting tension fluctuations when a joining point passes through a rolling stand using a prediction model learned by machine learning as a tension fluctuation prediction method for changing a running thickness. The prediction model described in Patent Document 2 uses rolling operation parameters of a preceding material and a rolling operation parameter change amount representing a difference value between the rolling operation parameters of the preceding material and the following material as input data, and tension fluctuation information when a joining point passes through a rolling stand as output data. On the other hand, Patent Document 3 describes a method for calculating an actuator change amount at the timing when a joining point passes through a rolling stand, and judging whether or not a running thickness change is possible based on the calculated actuator change amount and a predetermined threshold value. Patent Document 3 also describes that it is possible to easily judge whether or not a running thickness change is possible based on the actuator change amount in a rolling schedule calculation without the need to use a highly accurate tension fluctuation prediction model. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-249423 [Patent Document 2] Patent Publication No. 2022-21794 [Patent Document 3] JP 2019-111568 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the prediction accuracy of the tension fluctuation amount by the method described in Patent Document 1 is low. In detail, the thickness change while traveling is performed when the base material thickness, the finish thickness, or the deformation resistance is different between the leading material and the trailing material, but there are various combinations of the change amounts of the leading material and the trailing material for each rolling stand. In addition, the combination of the leading material and the trailing material is set according to the production schedule of the tandem rolling mill, and is not necessarily set to reduce the tension fluctuation amount in the thickness change while traveling. For this reason, even if a prediction means trained by a neural network using the actual value of the tension fluctuation amount as teacher data is used, the prediction accuracy of the tension fluctuation amount decreases when a combination of a leading material and a trailing material that has no past operating experience is set. On the other hand, Patent Document 1 describes that the prediction means uses a tension generation model determined based on a physical model. However, when the tension generation model is used, it is difficult to accurately calculate the tension fluctuation amount in a non-steady state in which the roll gap and roll peripheral speed are changed at the junction point between the leading material and the trailing material, and the base material thickness, the finish thickness, the deformation resistance, etc. change suddenly.

[0007] Similarly, the prediction model trained by machine learning described in Patent Document 2 also has a reduced prediction accuracy of tension fluctuation when a combination of a preceding material and a following material that has no past operating record is set. This is because there are many combinations of the rolling operation parameters of the preceding material and the rolling operation parameter change amount that represents the difference value of the rolling operation parameters of the preceding material and the following material. On the other hand, the method described in Patent Document 3 is a method for determining whether or not the thickness can be changed while the strip is in flight based on the actuator change amount that is correlated with the tension fluctuation amount, but it does not predict the tension fluctuation amount when the thickness is changed while the strip is in flight. For this reason, depending on the threshold value used for determining whether or not the thickness can be changed while the strip is in flight, it may not be possible to make an appropriate determination.

[0008] The present invention has been made to solve the above problems, and its object is to provide a method, an apparatus, and a program for determining whether or not to change the thickness while flying, which can accurately predict the amount of tension fluctuation when changing the thickness while flying, even under conditions where the combination of preceding and succeeding materials has little past operational experience, and can execute an appropriate determination of whether or not to change the thickness while flying. Another object of the present invention is to provide a method for changing the thickness while flying, which can suppress the occurrence of breakage, squeezing, etc. of the metal strip and can roll the metal strip with a good yield. [Means for solving the problem]

[0009] The method for determining whether or not the flying thickness can be changed according to the present invention is a method for determining whether or not the flying thickness can be changed when a rolled material in which a preceding material and a following material are joined via a joint is continuously rolled by a tandem rolling mill, and includes a setting value acquisition step for acquiring set values ​​of the roll gap and roll circumferential speed of the rolling stand for the preceding material before starting to change the set values ​​of the roll gap and roll circumferential speed in at least one rolling stand of the tandem rolling mill, a tension fluctuation calculation step for calculating the amount of tension fluctuation when the joint passes through the rolling stand while maintaining the set values ​​of the roll gap and roll circumferential speed for the preceding material, and a determination step for determining whether or not the flying thickness can be changed based on the tension fluctuation amount calculated in the tension fluctuation calculation step.

[0010] The tension fluctuation calculation step preferably calculates the tension fluctuation when the joint passes through the rolling stand while maintaining the set values ​​of the roll gap and roll circumferential speed for the preceding material, using the set values ​​of the roll gap and roll circumferential speed of the rolling stand for the preceding material acquired in the set value acquisition step, and the plate thickness and deformation resistance set for the following material passing through the rolling stand.

[0011] In the above-mentioned change in the running thickness, it is preferable that a start point of the change in the roll gap and the roll peripheral speed is set to the position of the preceding material, and an end point of the change in the roll gap and the roll peripheral speed is set to the position of the following material.

[0012] It is preferable that the difference between the deformation resistance of the preceding material and the deformation resistance of the following material is 80 MPa or more.

[0013] The method for changing the flying thickness of the present invention uses the method for determining whether or not the flying thickness can be changed of the present invention to perform a flying thickness change when it is determined that the flying thickness change is possible in all rolling stands of the tandem rolling mill, and when it is determined that the flying thickness change is not possible in at least one rolling stand of the tandem rolling mill, the set values ​​of the roll gap and roll peripheral speed of the rolling stand for the following material are changed.

[0014] The device for determining whether or not the thickness can be changed while the plate is in flight according to the present invention is a device for determining whether or not the thickness can be changed while the plate is in flight when a rolled material in which a preceding material and a following material are joined via a joint is continuously rolled by a tandem rolling mill, and comprises: a setting value acquisition means for acquiring the set values ​​of the roll gap and roll circumferential speed of the rolling stand for the preceding material before starting to change the set values ​​of the roll gap and roll circumferential speed in at least one rolling stand of the tandem rolling mill; a tension fluctuation calculation means for calculating the amount of tension fluctuation when the joint passes through the rolling stand while maintaining the set values ​​of the roll gap and roll circumferential speed for the preceding material; and a determination means for determining whether or not the thickness can be changed while the plate is in flight based on the tension fluctuation calculated by the tension fluctuation calculation means.

[0015] The program for determining whether or not the flying thickness can be changed according to the present invention is a program for determining whether or not the flying thickness can be changed when a rolled material in which a preceding material and a following material are joined via a joint is continuously rolled by a tandem rolling mill, and causes a computer to function as: a setting value acquisition means for acquiring the set values ​​of the roll gap and roll circumferential speed of the rolling stand for the preceding material before starting to change the set values ​​of the roll gap and roll circumferential speed in at least one rolling stand of the tandem rolling mill; a tension fluctuation calculation means for calculating the amount of tension fluctuation when the joint passes through the rolling stand while maintaining the set values ​​of the roll gap and roll circumferential speed for the preceding material; and a determination means for determining whether or not the flying thickness can be changed based on the amount of tension fluctuation calculated by the tension fluctuation calculation means. Effect of the Invention

[0016] According to the method, device, and program for determining whether or not the thickness can be changed while traveling, it is possible to accurately predict the amount of tension fluctuation when the thickness is changed while traveling even under conditions where the combination of the preceding and succeeding materials has little past operating experience, and to perform an appropriate determination as to whether or not the thickness can be changed while traveling. Furthermore, according to the method for changing the thickness while traveling according to the present invention, it is possible to suppress the occurrence of breakage, squeezing, etc. of the metal strip and to roll the metal strip with a good yield. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic diagram showing an example of the configuration of a continuous cold rolling facility to which the present invention is applied. [Diagram 2] FIG. 2 is a diagram showing the relationship between the delivery thickness of the rolled material and the roll gap. [Diagram 3] FIG. 3 is a diagram showing the relationship between the delivery thickness of the rolled material and the roll gap. [Figure 4] FIG. 4 is a flowchart showing the flow of setting calculation for the succeeding material during rolling of the preceding material. [Diagram 5] FIG. 5 is a diagram for explaining the start point and end point of the running thickness change. [Figure 6] FIG. 6 is a diagram for explaining a method for calculating the tension fluctuation index. [Figure 7] FIG. 7 is a flowchart showing the flow of a method for determining whether or not the running gauge can be changed according to one embodiment of the present invention. [Figure 8] FIG. 8 is a diagram for explaining the two-stage on-the-fly thickness change. [Figure 9] FIG. 9 is a diagram for explaining the start point and end point of the two-stage on-the-fly thickness change. [Figure 10] FIG. 10 is a diagram showing the fluctuation of the unit tension of the rolled material. [Figure 11] FIG. 11 is a diagram showing the relationship between the tension fluctuation index and the actual value of tension fluctuation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, with reference to the drawings, an embodiment of the present invention will be described, which relates to a method for determining whether or not a thickness can be changed while the ship is in flight, a method for changing the thickness while the ship is in flight, an apparatus for determining whether or not a thickness can be changed while the ship is in flight, and a program for determining whether or not a thickness can be changed while the ship is in flight.

[0019] [Configuration of continuous cold rolling equipment] First, with reference to FIG. 1, a configuration example of a continuous cold rolling facility to which the present invention is applied will be described.

[0020] Fig. 1 is a schematic diagram showing a configuration example of a continuous cold rolling facility to which the present invention is applied. In Fig. 1, other devices associated with the continuous cold rolling facility (for example, a rewinder, a welding machine, and a looper installed on the entry side, and a cutter, a winder, and other devices installed on the exit side) are omitted from the illustration. As shown in Fig. 1, the continuous cold rolling facility 1 to which the present invention is applied includes a tandem rolling mill 2, a rolling control controller (PLC) 3 that controls the tandem rolling mill 2, and a control computer (process computer) 4 that manages the continuous cold rolling facility 1 including the rolling control controller 3.

[0021] The tandem rolling mill 2 is a continuous cold tandem rolling mill having a first rolling stand 2A to a fifth rolling stand 2E in order from the entry side in the passing direction of the material 5 to be rolled. Each rolling stand is provided with a work roll 21, a roll circumferential speed control device 22 which is an electric motor for changing the roll circumferential speed of the work roll 21, and a roll gap control device 23 for changing the roll gap between the upper and lower work rolls 21. A rolling load detector 24 consisting of a load cell is provided under the lower backup roll of each rolling stand. Furthermore, each rolling stand is provided with a roll position detector 25 for detecting the roll position. Furthermore, a tension meter 26 for detecting the tension of the material 5 to be rolled is provided between each rolling stand. Furthermore, a thickness meter 27 for detecting the thickness (plate thickness) of the material 5 to be rolled is provided on the exit side of the first rolling stand 2A and the exit side of the fifth rolling stand 2E.

[0022] The rolling controller 3 collects rolling operation data such as the rolling load detected by the rolling load detector 24 and the tension detected by the tension meter 26 at a predetermined sampling period, and outputs the data to the control computer 4. The rolling controller 3 also executes processing for controlling the roll peripheral speed control device 22 and the roll gap control device 23 of each rolling stand based on each value acquired from the control computer 4. The rolling controller 3 also has a function of tracking the junction point of the preceding material and the succeeding material, as well as tracking a specified position on the material to be rolled 5. This allows the rolling controller 3 to output a command value for changing a predetermined set value to the control devices such as the roll peripheral speed control device 22 and the roll gap control device 23 at the timing when a preset position of the material to be rolled 5 including the junction point passes through each rolling stand of the tandem rolling mill 2.

[0023] The control computer 4 sets the rolling schedule and the flying thickness change unit described later, and generates command values ​​for changing the set values ​​of the roll gap and roll circumferential speed of each rolling stand corresponding to the flying thickness change unit. The command values ​​for changing the set values ​​of the roll gap and roll circumferential speed often use the difference between the set values ​​for the preceding material and the set values ​​for the succeeding material, which is called a difference command value. In addition, the control computer 4 calculates the pass schedule of the preceding material and the succeeding material, the predicted values ​​of the rolling load and forward ratio of each rolling stand, and the set values ​​of the roll gap and roll circumferential speed according to information such as the base material dimensions and the target product dimensions given by the upper computer. Then, the control computer 4 sets these calculated values ​​in the lower-level rolling controller 3.

[0024] [Relationship between roll gap and plate thickness] Next, the process of changing the setting of the roll gap from the preceding material to the succeeding material will be described with reference to Figs.

[0025] First, referring to FIG. 2, a general relationship between the roll gap of a rolling mill and the thickness of a rolled material will be described. In a rolling mill, the entire rolling mill is deformed in the vertical direction by the reaction force of the rolling load applied to the rolled material, and the preset roll gap widens. For this reason, in order to obtain a rolled material of a specified thickness, the roll gap must be set in consideration of the rolling load and the deformation amount of the rolling mill. FIG. 2 is a diagram showing the relationship between the exit thickness h of the rolled material and the roll gap S when rolling a rolled material with an entry thickness H of the rolling mill. As shown in FIG. 2, since the deformation of the rolling mill is an elastic deformation, the roll gap S increases approximately linearly with respect to the rolling load P. This characteristic is called the elastic characteristic curve of the rolling mill. On the other hand, a curve that connects the rolling loads P calculated from the two-dimensional rolling theory assuming various exit thicknesses h is called the plastic characteristic curve of the rolled material. In actual rolling, the exit thickness h of the rolled material is determined from the condition where the rolling loads P are balanced (the intersection of the curves shown in FIG. 2).

[0026] Next, the relationship between the exit thickness h and the roll gap S in the running thickness change will be described with reference to FIG. 3. FIG. 3 is a diagram showing the relationship between the exit thickness of the rolled material and the roll gap when the entry thickness of the preceding material is H1, the entry thickness of the following material is H2, the preceding material is a hard material (the slope of the plastic characteristic curve is large), and the following material is a soft material (the slope of the plastic characteristic curve is small). As shown in FIG. 3, in the running thickness change, the roll gap S is set to the first roll gap S1 for the preceding material so that the target exit thickness h1 is obtained. Then, when the joining point passes through the rolling stand, the plastic characteristic curve transitions from the plastic characteristic curve of the preceding material (hard material) to the plastic characteristic curve of the following material (soft material). As a result, when the roll gap S1 is maintained, the intersection point between the elastic characteristic curve and the plastic characteristic curve transitions from intersection point a to intersection point b. As a result, when the joining point passes through the rolling stand, the exit thickness of the following material changes to hc. On the other hand, when the roll gap for the trailing strip is changed to the second roll gap S2, the intersection between the elastic characteristic curve and the plastic characteristic curve shifts from intersection b to intersection c, the outlet thickness of the trailing strip becomes the target thickness h2, and the running thickness change is completed.

[0027] In the running thickness change, a roll gap change command is usually issued when the junction point reaches the rolling stand. However, since it takes a certain amount of time to change the roll gap, the passage through the junction point is usually completed before the roll gap change (from the first roll gap S1 to the second roll gap S2) is completed. Therefore, the thickness fluctuation before and after passing through the junction point is a path close to h1 → hc → h2 in a transient manner. This transient thickness fluctuation changes the mass flow balance in each rolling stand, causing large tension fluctuations. In particular, when the plastic characteristic curve changes significantly on either side of the junction point, the thickness fluctuation (h1 → hc) becomes significant. This is the reason why large tension fluctuations occur when the deformation resistance of the preceding and following materials is different.

[0028] [Calculation of roll gap and roll peripheral speed] Next, a method for calculating the roll gap and roll peripheral speed for the material being rolled in a tandem rolling mill will be described.

[0029] The calculation of the roll gap and roll peripheral speed is carried out by the control computer 4, which sets the pass schedule of the material to be rolled according to information such as the base material dimensions and the target product dimensions given by the upper computer, calculates the rolling load of each rolling stand, and calculates the corresponding set values ​​of the roll gap and roll peripheral speed. The pass schedule refers to the target value of the delivery thickness in each rolling stand of the tandem rolling mill.

[0030] Specifically, in the calculation of the roll gap S of the material to be rolled in a tandem rolling mill, the control computer 4 first obtains the entry thickness H and exit thickness h of the material to be rolled in the rolling stand to be calculated from the pass schedule of the material to be rolled (target value of the exit thickness h), and then uses two-dimensional rolling theory to obtain a predicted value of the rolling load P, for example, using the following formula (1). In formula (1), P is the rolling load (kN), k m is the average deformation resistance of the rolled material (MPa), R' is the radius of the flat roll (mm), H is the inlet thickness of the rolled material (mm), h is the outlet thickness of the rolled material (mm), b is the width of the rolled material (mm), Q P is the rolling force function, μ is the friction coefficient, q b is the entry tension (MPa), q f indicates the tension at the exit side (MPa). The flattened roll radius R' is calculated by applying Hitchcock's roll flattening equation and is obtained from a simultaneous solution with the load calculation based on two-dimensional rolling theory.

[0031]

number

[0032] Next, the control calculator 4 uses the predicted value of the rolling load P for the material being rolled calculated in this way to determine the set value S of the roll gap S, for example, by the following formula (2): Here, in formula (2), K is a mill constant (kN / mm) that represents the gradient of the elastic characteristic curve of the tandem rolling mill, and δ is a constant that is set for each tandem rolling mill.

[0033]

number

[0034] The control computer 4 executes the above calculations for all rolling stands of the tandem rolling mill to determine the roll gap setting value S for each rolling stand. Note that the roll gap setting value for an arbitrary rolling stand is represented as S, but the roll gap setting value for each rolling stand is represented as S(i) to indicate that it is the roll gap in the i-th rolling stand.

[0035] Next, the flow of calculation for setting the roll circumferential speed of each rolling stand will be explained. The calculation for setting the roll circumferential speed is executed at the same timing as the calculation for setting the roll gap. The roll circumferential speed indicates the circumferential speed of the work rolls of a tandem rolling mill. Specifically, the control computer 4 calculates the forward slip ratio f s The predicted value of is calculated using the following formula (3). The forward advance rate can be calculated, for example, from the Bland & Ford forward advance rate formula.

[0036]

number

[0037] At this time, the roll peripheral speed V R (i) (mm / s) satisfies the constant mass flow law shown in the following formula (4) in a steady state.

[0038]

number

[0039] In formula (4), i is the rolling stand number, h (i) is the exit thickness of the rolled material in the i-th rolling stand (mm), f s (i)indicates the forward slip (-) of the i-th rolling stand. This means that once the roll peripheral speed of an arbitrary rolling stand is determined, the roll peripheral speeds of the other rolling stands are determined by formula (4). Usually, the rolling speed when changing the thickness while traveling is preset in the range of approximately 100 to 400 m / min as the roll peripheral speed of the final rolling stand, and the roll peripheral speeds of the other rolling stands are also determined based on this. The above setting calculations are performed for each rolled material that is continuously rolled in the tandem rolling mill.

[0040] Next, with reference to FIG. 4, a flow of setting calculations when changing the running strip thickness in a tandem rolling mill will be described.

[0041] FIG. 4 is a flow chart showing the flow of setting calculation for the following material while the preceding material is being rolled. The set values ​​of the roll gap and roll circumferential speed for the preceding material have already been determined while the preceding material is being rolled. Therefore, the set values ​​of the roll gap and roll circumferential speed for the following material are calculated, and the change amount of the roll gap and the change amount of the roll circumferential speed (difference command value) are obtained as command values ​​when changing the thickness while traveling. In the following, the roll gap for the preceding material is S1, the roll circumferential speed is V R 1. In addition, the entry thickness of the target rolling stand for the preceding material is H1, the exit thickness is h1, the rolling load is P1, and the forward slip is f s 1. The deformation resistance of the preceding material is k m Similarly, the roll gap for the following material is denoted as S2, and the roll peripheral speed is V R 2, the entry thickness is H2, the exit thickness is h2, the rolling load is P2, and the forward slip is f s 2. The deformation resistance of the following material is k m In other words, at the time when the setting calculation for the following material shown in Figure 4 is started, the roll gap S1 and roll peripheral speed V R 1, entry plate thickness H1, exit plate thickness h1, deformation resistance k m 1, rolling load P1, and forward thrust f s 1 is specified in the control computer 4 and is stored in a storage device within the control computer 4.

[0042] In the setting calculation for the succeeding strip shown in Fig. 4, the control computer 4 sets the pass schedule (target value of the delivery thickness h2) for the succeeding strip according to information such as the base strip dimensions and product target dimensions of the succeeding strip given by the upper computer (step ST1). Next, the control computer 4 calculates the rolling load P2 of each rolling stand using the above formula (1), and calculates the forward ratio f s Then, the control computer 4 calculates the set value of the roll gap S2 for the following material using the formula (2), and calculates the roll peripheral speed V for the following material using the formula (4). R 2 (step ST2). As a result, the roll gap S2 and roll peripheral speed V R The set values ​​of roll gap S1 and roll peripheral speed V2 for the preceding material are specified. R The setting calculation of 1 has already been completed. Therefore, the roll gap S1 and roll peripheral speed V of the preceding material are stored in the storage device of the control computer 4. R By acquiring the set value of 1, the roll gap and roll peripheral speed difference command values ​​are specified (step ST3). The roll gap change amount ΔS, which is the roll gap difference command value, is calculated by the following formula (5).

[0043]

number

[0044] Similarly, the roll circumferential speed change amount ΔV R is calculated using the following formula (6).

[0045]

number

[0046] The difference command values ​​of the roll gap and roll peripheral speed calculated as above are sent to the rolling controller 3 based on the tracking information of the joining point. The calculations up to this point are executed before the start of the running thickness changing process. The roll gap S1 and roll peripheral speed V of the preceding material stored in the storage device in the control computer 4 are also sent to the rolling controller 3. R The set value of roll gap S1 and roll peripheral speed V may be calculated based on the set value of the preceding material. Also, the rolling controller 3 collects the actual values ​​of the roll gap and roll peripheral speed during rolling of the preceding material (called lock-on), and uses the collected values ​​as the roll gap S1 and roll peripheral speed V R In some cases, the setting value is stored in the storage device as 1. This makes it possible to obtain a setting value that reflects the latest rolling state of the preceding material.

[0047] [Start and end points of thickness change during flight] Next, the start and end points of the running gauge change will be described with reference to Figs. 5(a) to (c).

[0048] The start point of the flying thickness change is set near the joint (joint point) W between the leading and trailing materials, and is the start point of the change in the roll gap and roll circumferential speed. Changing the roll gap and roll circumferential speed takes a certain amount of time, and the time from the start to the end of the change in the roll gap and roll circumferential speed in each rolling stand is called the flying thickness change time. The flying thickness change time is often set to be the same for all rolling stands. The position where the change in the roll gap and roll circumferential speed in the longitudinal direction of the rolled material is completed corresponding to the flying thickness change time is the end point of the flying thickness change, and the section from the start point to the end point of the flying thickness change is sometimes called the flying thickness change section.

[0049] FIG. 5(a) shows an example in which the start point FS is set on the tail end side of the preceding material A and on the upstream side of the junction point W, and the end point FE is the position of the front end of the following material B. In this case, the junction point W passes through the rolling stand after the start of the change in the roll gap and the roll circumferential speed but before the end of the change. Therefore, while the intersection of the elastic characteristic curve and the plastic characteristic curve shown in FIG. 3 is transitioning from point a to point d, the transition from the plastic characteristic curve of the preceding material A to the plastic characteristic curve of the following material B occurs. FIG. 5(b) shows an example in which the start point FS and the end point FE are both set on the tail end side of the preceding material A. In this case, the junction point W passes through the rolling stand after the change in the roll gap and the roll circumferential speed is completed. Therefore, the intersection of the elastic characteristic curve and the plastic characteristic curve shown in FIG. 3 is transitioned from point a to point d, and then transitions from point d to point c. FIG. 5(c) shows an example in which the start point FS and the end point FE are both set on the front end side of the following material B. In this case, the junction point W passes through the rolling stand before the start of changes in the roll gap and roll peripheral speed. Therefore, the intersection point between the elastic characteristic curve and the plastic characteristic curve shown in Fig. 3 transitions from point a to point b, and then from point b to point c.

[0050] As described above, when changing the thickness while traveling, the behavior of the transition of the intersection of the elastic characteristic curve and the plastic characteristic curve changes depending on the positional relationship between the start point FS and the end point FE and the junction point W, and the corresponding fluctuation in mass flow causes complex changes in the tensions at the entry and exit of the rolling stand.

[0051] The running thickness change time required to change the roll gap and roll peripheral speed to execute the running thickness change is determined, for example, as follows. The roll gap change speed of each rolling stand differs depending on whether the rolling down device is hydraulic or electric, but is set, for example, to 0.5 to 2 mm / s for hydraulic rolling down and 0.2 to 0.8 mm / s for electric rolling down. In this case, the time required to change the roll gap of each rolling stand can be calculated by dividing the absolute value of the roll gap change amount ΔS by the roll gap change speed (|ΔS| ÷ roll gap change speed). However, since tension fluctuation can be reduced by standardizing the running thickness change time for all rolling stands, the longest running thickness change time among the running thickness change times required for each rolling stand is adopted. In an actual tandem rolling mill, the running thickness change time is usually about 0.2 to 2.5 seconds. The running thickness change time may be determined for each rolling condition of the preceding and succeeding strips, but may also be preset in the control computer 4 as a fixed value.

[0052] When the running thickness change time is determined, the running thickness change time is converted into the length of the rolled material from the conveying speed at the entry side of the rolling mill, and this can be specified as the running thickness change section. The length of the joint (length in the conveying direction) is approximately 1 to 100 mm at the entry side of the tandem rolling mill. For example, if the length of the joint is 10 mm and the conveying speed at the entry side of the tandem rolling mill is assumed to be 60 m / min, the time for the joint to pass through the first rolling stand 2A is as extremely short as 0.01 seconds. That is, since the length of the joint is short compared to the running thickness change section, the length of the joint is ignored in practice and is called the joint "point."

[0053] [Method of determining whether or not the running thickness can be changed] A method for determining whether or not the running thickness can be changed, which is one embodiment of the present invention, includes a setting value acquisition step of acquiring set values ​​of the roll gap and roll circumferential speed for the preceding material before starting to change the settings of the roll gap and roll circumferential speed in at least one rolling stand of a tandem rolling mill, a tension fluctuation calculation step of calculating the amount of tension fluctuation when the joint passes through the rolling stand while maintaining the set values ​​of the roll gap and roll circumferential speed for the preceding material, and a judgment step of judging whether or not the running thickness can be changed based on the tension fluctuation amount calculated in the tension fluctuation calculation step.

[0054] The set value acquisition step acquires the set values ​​of the roll gap and roll peripheral speed for the preceding material before the start point of the thickness change on the fly reaches the rolling stand where the thickness change on the fly is performed. The set values ​​of the roll gap and roll peripheral speed are the roll gap S1 and roll peripheral speed V of the preceding material stored in the storage device in the control computer 4. R The set values ​​of the roll gap S1 and the roll peripheral speed V1 can be used. In addition, the rolling controller 3 collects actual values ​​of the roll gap and the roll peripheral speed during rolling of the preceding material, and calculates these values ​​as the roll gap S1 and the roll peripheral speed V2. R Alternatively, the value stored in the storage device may be acquired again as 1.

[0055] The tension fluctuation calculation step is to calculate the roll gap S1 and roll peripheral speed V R The tension fluctuation amount is calculated when the joint point W passes through the rolling stand while maintaining the set value of 1. As described above, in the running thickness change, when the joint point W passes through the rolling stand, the roll gap and roll peripheral speed are changed according to the command of the difference amount set in the setting calculation. However, in the tension fluctuation calculation step, the roll gap S1 and roll peripheral speed V RThe tension fluctuation amount is calculated for a virtual state in which the joining point W passes through the rolling stand while maintaining the set value of 1. The tension fluctuation amount calculated in this manner is hereinafter referred to as the tension fluctuation index. The tension fluctuation index is not calculated by accurately simulating an actual on-the-fly thickness change, but it is an index that has a high correlation with the tension fluctuation that occurs in an actual on-the-fly thickness change when there is a difference in thickness or deformation resistance at the entry side of the rolling stand between the leading and trailing strips. For this reason, it is possible to accurately determine whether or not to change the on-the-fly thickness based on the tension fluctuation index. The method for calculating the tension fluctuation index will be described later.

[0056] The determination step determines whether the thickness can be changed while the strip is in flight based on the tension fluctuation index calculated in the tension fluctuation amount calculation step. The tension fluctuation index has a high correlation with the tension fluctuation amount when the roll gap and roll peripheral speed are changed according to the set difference amount in the thickness change while the strip is in flight. Therefore, it is possible to determine whether the tension fluctuation amount becomes excessive before the joining point passes through the rolling stand, and it is possible to prevent operational trouble caused by tension fluctuation. The determination of whether the thickness can be changed while the strip is in flight in the determination step may be performed, for example, by setting a threshold value for the tension fluctuation index in advance, and determining that the thickness can be changed while the strip is in flight if the tension fluctuation index calculated in the tension fluctuation amount calculation step is equal to or less than the threshold value, and determining that the thickness cannot be changed while the strip is in flight if the tension fluctuation index exceeds the threshold value.

[0057] [Tension fluctuation index] The tension fluctuation index calculated in the tension fluctuation calculation step can be calculated by applying the basic equations used in the continuous rolling theory using a physical model in which physical phenomena are modeled by differential equations, etc. In this case, if the roll gap and roll peripheral speed change according to a set difference amount along with the behavior of the joint passing through the rolling stand, a numerical simulation is required to solve the differential equation every minute time. However, if the roll gap and roll peripheral speed are constant, the tension fluctuation amount can be easily obtained.

[0058] Figure 6 shows three adjacent rolling stands that make up a tandem rolling mill. Figure 6 shows the state when the junction point W passes through the N stand after reaching between the N-1 stand and the N stand. In other words, the roll gap S1 and roll peripheral speed V set for the preceding material in the N stand and the N+1 stand are R Rolling is performed at stand N-1, and the roll gap S2 and roll peripheral speed V R At No. 2, rolling is taking place.

[0059] In this embodiment, the tension fluctuation index is, for example, the roll gap S1 and the roll peripheral speed V R Calculate the amount of tension fluctuation that occurs on the entry side or exit side of N stand when junction point W passes through N stand while maintaining the set value of 1. In this case, since the amount of tension fluctuation that occurs when junction point W passes through N stand is larger on the entry side than on the exit side of N stand, the tension fluctuation index can be the amount of tension fluctuation that occurs on the entry side of N stand (between N-1 stand and N stand).

[0060] The physical model for calculating the tension q (MPa) at the entrance of the N stand can generally be expressed by the following formula (7). In formula (7), L is the distance between the rolling stands (m), E is the Young's modulus of the rolled material (MPa), v in,N (m / s) is the material speed at the entrance of the N stand, v out,N-1 (m / s) represents the material speed of the rolled material at the exit of N-1 stand, and t represents time (s).

[0061]

number

[0062] In other words, the tension q at the entrance of the N stand can be calculated by integrating the difference between the speed of the rolled material discharged from the upstream rolling stand and the speed of the rolled material flowing into the downstream rolling stand, and converting this into the elastic strain between the rolling stands. In this case, the roll gap S2 and roll peripheral speed V set for the following material in the N-1 stand are R When rolling is performed at stand N-1, the material speed of the rolled material at the exit of stand N-1 is v out,N-1 Since is considered to be roughly constant, the change dq in the tension q at the entrance side of the N stand can be expressed as the following formula (8).

[0063]

number

[0064] Here, the change in material speed of the rolled material at the inlet of N stand in formula (8) is dv in,N changes according to the change in the rolling state in the N stand. In other words, when the joint point W passes through the N stand, the thickness and deformation resistance of the rolled material change, and it also changes from time to time as the roll gap and roll peripheral speed of the N stand are changed. Therefore, to accurately obtain the amount of tension fluctuation between rolling stands, a numerical simulation is required to solve a differential equation at every minute time in response to the behavior of the joint point passing through the rolling stands and the change in the settings of the roll gap and roll peripheral speed.

[0065] In contrast, the tension fluctuation index used in this embodiment is the roll gap S1 and the roll peripheral speed V R Calculate the amount of change in tension q that occurs at the entry side of N stand when the joining point W passes through N stand while maintaining the set value of 1. For this purpose, calculate the amount of change in material speed dv of the rolled material at the entry side of N stand due to the change in the roll gap and roll peripheral speed settings. in,NIn addition, since the time it takes for the joint point W to pass through the N stand is extremely short, about 0.01 seconds, as mentioned above, the time step dt in formula (8) can be replaced with a calculation of one step (time step Δt) to express the change Δq in the tension q at the entrance of the N stand as shown in formula (9) below. Here, in formula (9), Δv in,N is the roll gap S1 and the roll peripheral speed V R The material speed v of the rolled material at the inlet of N stand when rolling the preceding material is set as the set value of 1. 1 and the set values ​​of roll gap and roll peripheral speed S1, V R 1, the material speed of the rolled material at the entrance of N stand when rolling the following material v 2 The amount of change Δq in tension q calculated in this manner is the tension fluctuation index in this embodiment.

[0066]

number

[0067] Roll gap S1 and roll peripheral speed V R When rolling the preceding material with the setting value of 1, the exit thickness h1 at the N stand is calculated from the intersection a between the elastic characteristic curve of the N stand and the plastic characteristic curve of the preceding material in the setting calculation (Fig. 3). In addition, the corresponding forward ratio f 1 Therefore, the roll gap S1 and the roll peripheral speed V R The material speed v of the rolled material at the entrance of N stand when rolling the preceding material is set as the set value of 1. 1 can be calculated by the following formula (10).

[0068]

number

[0069] On the other hand, the roll gap S1 and roll peripheral speed V RWhen rolling the following material while maintaining the set value of 1, the exit thickness hc at N stand is calculated by multiplying the entry thickness H2 of N stand by the deformation resistance k m 2, it can be calculated as a simultaneous solution of the rolling load calculated from formula (1) and formula (2) which expresses the elastic characteristic curve of N stand. That is, it can be obtained from the intersection point b in Figure 3. And the corresponding forward ratio f c can also be calculated by applying formula (3). Therefore, the roll gap S1 and the roll peripheral speed V R The material speed v of the rolled material at the entrance of stand N when rolling the following material while maintaining the setting value of 1. 2 can be calculated by the following formula (11).

[0070]

number

[0071] From the above, the material speed v of the rolled material at the entrance of N stand 1 and material velocity v 2 Using this, Δv in Eq. (9) in,N can be obtained. In addition, Δt in formula (9) is a value representing the time when the junction point W passes through the N stand, and can be calculated using the length of the junction point W and the material speed of the rolled material passing through the rolling stand. However, Δt in formula (9) may be set arbitrarily in the range of 0.005 to 0.050 seconds in practice. Even if the time step Δt used in formula (9) differs from the actual time when the junction point W passes through the N stand, it can be used as an index reflecting the magnitude of the tension fluctuation amount. For example, when the operation is performed in a constant range of the length of the junction point W between the preceding and following strips, and the rolling speed at which the running thickness change is performed is approximately constant, even if Δt is set to an arbitrary value, it can be used as an index for evaluating the magnitude of the tension fluctuation when the junction point W passes through the rolling stand. On the other hand, Δt is calculated by assuming that the length of the junction point W is constant and the material speed v in the N stand. 1 and roll circumferential speed V R It is also possible to set it as a function inversely proportional to 1 and apply this to equation (9).

[0072] As described above, the tension fluctuation index in this embodiment is the roll gap S1 and the roll peripheral speed V R When rolling the preceding material by 1, the inlet material speed v 1 , roll gap S1 and roll peripheral speed V R The inlet material speed v when it is assumed that the succeeding material is rolled while maintaining 1. 2 This makes it possible to obtain an index representative of tension fluctuations extremely easily, compared to a method of predicting tension fluctuations that involves integral calculations at short time intervals, such as the method of performing a numerical simulation using formulas (7) and (8).

[0073] In the tension fluctuation calculation step of this embodiment, as described above, the roll gap S1 and roll peripheral speed V of the rolling stand for the preceding material acquired in the set value acquisition step are R 1, and the entry thickness H2 and deformation resistance k set for the succeeding strip passing through N stand m 2, the roll gap S1 and roll peripheral speed V R It is preferable to calculate the amount of tension fluctuation when the joining point W passes through N stand while maintaining the set value of 1.

[0074] In addition, the flying thickness change of this embodiment is preferably applied when the start point of the change of the roll gap and the roll circumferential speed (start point FS of the flying thickness change) is set for the preceding material, and the end point of the change of the roll gap and the roll circumferential speed (end point FE of the flying thickness change) is set for the following material in at least one rolling stand (N stand) of the tandem rolling mill. That is, it is preferably applied when the junction point W passes through the N stand in the flying thickness change section as shown in FIG. 5(a). In the embodiment of the flying thickness change shown in FIG. 5(a), a transition from the plastic characteristic curve of the preceding material to the plastic characteristic curve of the following material occurs during the transition of the intersection of the elastic characteristic curve and the plastic characteristic curve from point a to point d as shown in FIG. 3, and the behavior of the actual tension fluctuation becomes complicated, but even in such a case, the magnitude of the tension fluctuation can be estimated by a simple method.

[0075] Furthermore, the method for determining whether or not the thickness of a running strip can be changed according to the above embodiment is m 1 and the deformation resistance k of the succeeding material m 2 is preferably applied when the difference between the preceding and following strips is 80 MPa or more. The greater the difference in deformation resistance between the preceding and following strips, the greater the deviation of the plastic characteristic curves shown in FIG. 3 between the preceding and following strips, and the greater the actual tension fluctuation. Therefore, in a method using a numerical simulation to calculate tension fluctuations at minute time intervals, it is necessary to set the time step finely, which increases the calculation time. In addition, in actual operation, since the thickness change during running is rarely performed under conditions where the difference between the deformation resistance of the preceding strip and the deformation resistance of the following strip is large, it is difficult to obtain a sufficient number of actual data, and high accuracy cannot be obtained by predicting tension fluctuations using machine learning. In contrast, the tension fluctuation index according to this embodiment can ensure a relatively high estimation accuracy of tension fluctuations in a simple manner.

[0076] Here, we will explain the causes of tension fluctuations when the joint passes through the rolling stand during the thickness change on the fly. The causes of tension fluctuations that occur during the thickness change on the fly can be roughly divided into two categories. The first cause is due to tracking errors at the joint and response delays in the roll gap and roll circumferential speed. When tracking errors at the joint and response delays in the roll gap and roll circumferential speed occur, a deviation occurs between the theoretically assumed speed of the material to be rolled and the actual speed. This causes the mass flow of the material to be rolled to fluctuate, which causes tension fluctuations. Therefore, the larger the change amount (difference command value) of the roll gap and roll circumferential speed during the thickness change on the fly, the greater the tension fluctuations. The second cause is tension fluctuations caused by the difference in the entry thickness and deformation resistance of the rolling stands of the preceding and following materials before and after the joint. At the moment when the joint reaches the N stand, the rolling state of the N stand changes suddenly. For example, when a soft preceding material is replaced by a hard succeeding material, the rolling load in the N stand increases rapidly, and the actual roll gap opens due to the elastic deformation of the rolling mill, causing the exit thickness of the N stand to increase. Then, the entry speed v in,Nincreases, and the tension between stand N-1 and stand N increases rapidly. In other words, tension fluctuation occurs when passing through the joint point, even if the roll gap or roll peripheral speed settings are not changed.

[0077] The tension fluctuation index of this embodiment focuses on the second cause. That is, when the first cause is taken into consideration, a numerical simulation is required to calculate an integral formula every minute time, whereas the tension fluctuation can be calculated by a very simple method for the second cause. As a result, the tension fluctuation index of this embodiment can be calculated by simply adding one virtual setting calculation for the following material. On the other hand, the tension fluctuation index of this embodiment does not consider the first cause. However, the first cause is caused by a tracking error at the joining point, a response delay in the roll gap and roll peripheral speed, etc., and becomes relatively smaller than the second cause as the performance of the control equipment of the tandem rolling mill improves. In particular, when the difference in deformation resistance between the preceding material and the following material is large, the influence of the first cause becomes smaller than the influence of the second cause. Therefore, under such conditions, even if the tension fluctuation in the running thickness change is estimated based on the second cause, the magnitude of the tension fluctuation can be appropriately determined.

[0078] [How to change plate thickness while traveling] The method for changing the flying thickness of this embodiment is a method for continuous rolling of rolled material to which the above-mentioned method for determining whether the flying thickness can be changed is applied, and when the determination step determines that the flying thickness can be changed in all rolling stands of the tandem rolling mill, the flying thickness change is carried out, and when the determination step determines that the flying thickness change is not possible in at least one rolling stand of the tandem rolling mill, the set values ​​of the roll gap and roll peripheral speed of the rolling stand for the following material are changed.

[0079] The method for changing the flying thickness of this embodiment will be described with reference to Fig. 1. In the method for changing the flying thickness of this embodiment, a determination is made as to whether or not the flying thickness can be changed while the preceding material is being rolled in all rolling stands 2A to 2E of the tandem rolling mill 2. For example, when the junction point between the preceding material and the following material reaches a junction point detection device (not shown) provided upstream of the tandem rolling mill 2, the control computer 4 executes setting calculations for the following material, and determines the roll gap S2 and roll peripheral speed V for the following material. R 2. When the joint detection device detects the joint, the rolling controller 3 starts tracking of the joint in the tandem rolling mill 2 based on the detected signal. Meanwhile, the control computer 4 executes setting calculations for the succeeding material, and also performs calculations for executing the above-mentioned method for determining whether or not the flying strip thickness can be changed. Specifically, the control computer 4 executes setting value acquisition step ST11, tension fluctuation amount calculation step ST12, and determination step ST13 shown in FIG. 7 for all the rolling stands 2A to 2E. Then, when it is determined that the flying strip thickness can be changed in all the rolling stands 2A to 2E, the control computer 4 calculates the differential command amounts ΔS, ΔV specified by the setting calculations. R On the other hand, if it is determined in the judgment step that the thickness change is not possible in at least one rolling stand of the tandem rolling mill, the control computer 4 changes the rolling conditions for the succeeding strip to the preset conditions (roll gap S2, roll peripheral speed V R 2) and pass the junction according to the changed conditions.

[0080] The condition to be changed when it is determined in the determination step that the running thickness change is not possible in at least one rolling stand of the tandem rolling mill is a condition that reduces the tension fluctuation when the joining point passes through the rolling stand. Specifically, a gap opening plate may be implemented in which the roll gaps of all rolling stands of the tandem rolling mill are opened to allow the joining point to pass without rolling the joining point. Also, the pass schedule for the following material may be changed from the preset one to allow the following material to pass through the joining point.

[0081] [Device and program for determining whether or not the thickness can be changed while traveling] Next, a description will be given of an apparatus and program for determining whether or not the above-mentioned flying thickness change is possible.

[0082] The device for determining whether or not the thickness can be changed while traveling according to the present embodiment is composed of a general-purpose computer such as a workstation or a personal computer, and is connected to the control computer 4 so as to be able to communicate with the control computer 4. The device for determining whether or not the thickness can be changed while traveling acquires information necessary for processing from the control computer 4, and outputs the result of the determination of whether or not the thickness can be changed while traveling to the control computer 4. The device for determining whether or not the thickness can be changed while traveling includes a set value acquisition means, a tension fluctuation calculation means, and a determination means. The set value acquisition means acquires the set values ​​of the roll gap and roll circumferential speed of the rolling stand for the preceding material from the control computer 4 before starting to change the set values ​​of the roll gap and roll circumferential speed in at least one rolling stand of the tandem rolling mill. The tension fluctuation calculation means calculates the tension fluctuation amount when the joint passes through the rolling stand while maintaining the set values ​​of the roll gap and roll circumferential speed for the preceding material. The determination means determines whether or not the thickness can be changed while traveling based on the tension fluctuation amount calculated by the tension fluctuation calculation means, and outputs the result of the determination of whether or not the thickness can be changed while traveling to the control computer 4.

[0083] The method for determining whether or not the thickness can be changed while the running is possible can also be realized by a computer executing a program. In addition, a computer-readable recording medium having the program recorded thereon and a computer program product of the program can also be applied as embodiments of the present invention. Examples of the recording medium that can be used include a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a magnetic tape, a non-volatile memory card, and a ROM.

[0084] The program for determining whether or not the thickness can be changed while flying according to the present embodiment may be configured to execute the steps of the method for determining whether or not the thickness can be changed while flying on a computer. In this case, the program for determining whether or not the thickness can be changed while flying on a general-purpose computer such as a workstation or a personal computer is executed, so that the general-purpose computer functions as a device for determining whether or not the thickness can be changed while flying. Furthermore, the program for determining whether or not the thickness can be changed while flying on a control computer 4 is loaded on the control computer 4, so that the control computer 4 can execute the processing of the method for determining whether or not the thickness can be changed while flying on the control computer 4.

[0085] [Other embodiments of thickness change during running] The above-mentioned method for determining whether or not the thickness change is possible while the plate is in flight and the method for changing the thickness while the plate is in flight can also be applied to two-stage thickness change while the plate is in flight, in which the thickness of the rolled material joined through a joining point is changed in two stages. Two-stage thickness change while the plate is in flight refers to a thickness change while the plate is in flight, in a tandem rolling mill that rolls a rolled material having a joining point between a leading material and a following material, in which the plate moves from rolling the leading material through an intermediate step to rolling the following material. Two-stage thickness change while the plate is in flight will be explained using Figure 8.

[0086] As shown in FIG. 8, in the two-stage running thickness change, first, the roll gap S is set to the first roll gap S1 for the preceding material so that the target delivery thickness h1 is obtained, and the second roll gap S2 is set for the following material so that the target delivery thickness h2 is obtained. In the two-stage running thickness change, the intermediate roll gap Sc in the intermediate step is further set. The intermediate step refers to a process (roll gap holding process) in which rolling is performed with roll gaps different from the first roll gap S1 and the second roll gap S2 in the process of transitioning from the preceding material to the rolling of the following material. In addition, the process of transitioning from the rolling of the preceding material to the intermediate step is called the first running thickness change process, and the process of transitioning from the intermediate step to the rolling of the following material is called the second running thickness change process. When performing the two-stage running thickness change, the intermediate roll gap Sc and the intermediate roll peripheral speed Vc corresponding to the delivery thickness hc in the intermediate step are calculated by setting calculation in the control computer 4 before the joining point reaches the rolling stand.

[0087] In the example shown in FIG. 8, when the first running thickness changing process is performed during the rolling of the preceding material, the intersection between the elastic characteristic curve and the plastic characteristic curve transitions from intersection a to intersection b due to the roll gap change (S1→Sc). As a result, the thickness at the exit of the rolling stand changes from h1 to hc1. Also, when the junction passes through the rolling stand in this state, the plastic characteristic curve changes before and after the junction, so the intersection between the elastic characteristic curve and the plastic characteristic curve transitions from intersection b to intersection c. As a result, the thickness at the exit of the rolling stand changes from hc1 to hc2. After that, when the second running thickness changing process is performed, the intersection between the elastic characteristic curve and the plastic characteristic curve transitions from intersection c to intersection d due to the roll gap change (Sc→S2). As a result, the thickness at the exit of the rolling stand changes from hc2 to h2, and the running thickness change is completed.

[0088] In the two-stage on-the-fly thickness change, the transitional thickness change at the delivery side of the rolling stand is h1→hc1→hc2→h2, and compared with the transitional thickness change h1→hc'→h2 in the one-stage on-the-fly thickness change without an intermediate step, the thickness change in the transition process is smaller and mass flow fluctuations are suppressed. Therefore, tension fluctuations are mitigated. In this embodiment, the feasibility of on-the-fly thickness change is determined on the premise of such two-stage on-the-fly thickness change. Hereinafter, the start point and end point of the two-stage on-the-fly thickness change will be described with reference to Figs. 9(a) and (b).

[0089] FIG. 9(a) shows an example in which the start point FS1 of the first flying thickness changing process is set to the preceding material A, and the end point FE1 of the first flying thickness changing process is set to the following material B. The start point FS2 and end point FE2 of the second flying thickness changing process are both set to the following material B. In this case, tension fluctuations become large in the first flying thickness changing process in which the roll gap and roll peripheral speed are changed via the joint point W, so it is preferable to apply the determination of whether or not the flying thickness can be changed in this embodiment to the first flying thickness changing process. When determining whether or not the flying thickness can be changed for the first flying thickness changing process, the parameters (S2, V R 2, h2) to the parameters of the intermediate step (Sc, V Rc, hc2) to calculate the tension fluctuation index. In this case, the deformation resistance of the rolled material in the intermediate step is calculated by replacing the deformation resistance k m Specifically, before starting the first running thickness change process, the roll gap S1 and roll peripheral speed V R Next, in the tension fluctuation calculation step, the roll gap S1 and roll peripheral speed V R The amount of tension fluctuation when the joining point W passes through the rolling stand while maintaining the set value of 1 is calculated as the intermediate step parameters Sc, V R c, hc2 are used for the calculation. Based on the tension fluctuation amount calculated in this way, a determination step is executed to determine whether or not the running thickness can be changed.

[0090] On the other hand, as shown in FIG. 9(b), the determination of whether or not the on-the-fly thickness change is possible in this embodiment can also be applied to a two-stage on-the-fly thickness change in which the start point FS1 of the first on-the-fly thickness change process, the end point FE1 of the first on-the-fly thickness change, and the start point FS2 of the second on-the-fly thickness change process are set to the preceding material A, and the end point FE2 of the second on-the-fly thickness change process is set to the following material B. In this case, since tension fluctuations become large in the second on-the-fly thickness change process in which the roll gap and roll peripheral speed are changed via the joint point W, it is preferable to apply the determination of whether or not the on-the-fly thickness change is possible in this embodiment to the second on-the-fly thickness change process. When the determination of whether or not the on-the-fly thickness change is possible in the second on-the-fly thickness change process, the parameters (S1, V R 1, h1) to the parameters of the intermediate step (Sc, V R c, hc2) to calculate the tension fluctuation index. In this case, the deformation resistance of the rolled material in the intermediate step is the deformation resistance k m Specifically, before starting the second running thickness change process, the roll gap Sc and roll peripheral speed V for the intermediate step are obtained in the setting value acquisition step. R Next, in the tension fluctuation calculation step, the roll gap Sc and roll peripheral speed V for the intermediate step are obtained. RThe amount of tension fluctuation when the joining point W passes through the rolling stand while maintaining the set value of c is calculated by the parameters S2 and V of the succeeding material B. R 2, h2 are used for calculation. A determination step is then executed to determine whether or not the on-the-fly thickness change is possible based on the tension fluctuation amount calculated in this manner. As a result, the magnitude of tension fluctuation in the two-stage on-the-fly thickness change can be appropriately determined. EXAMPLES

[0091] An embodiment of the present invention will be described. In this embodiment, a judgment was made as to whether or not the flying thickness change can be performed for one stage of the flying thickness change using a tandem rolling mill 2 having five rolling stands as shown in FIG. 1. The specifications of the tandem rolling mill 2 are as follows. The rolling load detector 24, the reduction position detector 25, the tension meter 26, and the thickness meter 27 were arranged at the positions shown in FIG. 1.

[0092] Maximum line speed: 2000mpm (m / min) Work roll diameter: 500~600mmφ Backup roll diameter: 1300~1400mmφ Distance between stands: 4600mm

[0093] First, the tension fluctuation index of the present invention was compared with the actual value of tension fluctuation due to the change in thickness during travel. The tension fluctuation index was evaluated based on the tension fluctuation occurring between the first rolling stand 2A and the second rolling stand 2B when the joint point W passes through the second rolling stand 2B of the tandem rolling mill 2. The rolled material for which tension fluctuation was evaluated had a mother plate thickness of 2.4 to 7.0 mm and a plate thickness at the exit of the final rolling stand of 0.5 to 3.6 mm. The plate width of the rolled material was 760 to 1900 mm, and included steel types ranging from low carbon steel to high strength steel plates with a tensile strength of 1180 MPa class for cold rolled steel sheet products. The deformation resistance difference between the preceding material and the succeeding material was in the range of -200 to +200 MPa. In calculating the tension fluctuation index, the time step Δt used in the formula (9) was set to 0.023 s based on the length of the joint point W. The roll gap and roll peripheral speed of the second rolling stand 2B for the preceding material acquired in the set value acquisition step were set values ​​held by the control computer 4. On the other hand, as the actual value of tension fluctuation due to the flying thickness change, the tension fluctuation amount (amplitude of tension fluctuation) measured in the flying thickness change process of the second rolling stand 2B was acquired from the fluctuation of the tension per unit cross-sectional area (unit tension) of the rolled material shown in Figure 10. The unit tension was calculated from the total tension using the thickness and width at the inlet side of the second rolling stand 2B.

[0094] Figure 11 shows the result of comparing the tension fluctuation index calculated by the above method with the actual value of tension fluctuation caused by the running thickness change. As shown in Figure 11, there is a high correlation between the tension fluctuation index calculated by the tension fluctuation calculation step and the actual value of tension fluctuation. In this case, the correlation coefficient between the tension fluctuation index and the actual value of tension fluctuation was 0.67, and the RMSE (root mean square error) was 1.7 MPa. In addition, when only the combinations of the preceding and following materials in which the deformation resistance difference between the preceding and following materials is 80 MPa or more in absolute value were extracted from the data shown in Figure 11 and the correlation coefficient was calculated again, it was 0.92. In addition, in the combinations of the preceding and following materials in which the deformation resistance difference between the preceding and following materials is 80 MPa or more in absolute value, the tension fluctuation is large, but the RMSE is suppressed to 2.1 MPa. From the above, it was confirmed that the tension fluctuation index calculated by the above method has a high correlation, especially when the difference in deformation resistance between the preceding and following materials is large.

[0095] Next, the results of the judgment of whether or not the thickness of the running strip can be changed using the tandem rolling mill 2 will be described. In this embodiment, the dimensions of the rolled material were set to a mother thickness of 2.4 to 3.6 mm, a thickness at the exit of the final rolling stand of 0.9 to 2.0 mm, and a width of 700 to 1400 mm. Here, the judgment of whether or not the thickness of the running strip can be changed was performed when the preceding and succeeding strips were a combination of high-strength steel sheets with tensile strengths of 590 MPa and 1180 MPa. In the past, with these combinations of preceding and succeeding strips, there was a high risk of the rolled material breaking due to excessive tension fluctuations, so a gap-opening strip was implemented by opening the roll gaps of all rolling stands and allowing the strip to pass without rolling the joints.

[0096] In the embodiment, a judgment is made as to whether or not the thickness can be changed while the rolling is in progress at all rolling stands, and if it is judged that the thickness can be changed while the rolling is in progress at all rolling stands in the judgment step, the thickness is changed while the rolling is in progress, and if it is judged that the thickness cannot be changed while the rolling is in progress at least at one rolling stand, the gap opening plate is performed. In the judgment step of this embodiment, if the tension fluctuation index calculated in the tension fluctuation calculation step is 30% or less of the set value of the interstand tension set for the preceding material, it is judged that the thickness can be changed while the rolling is in progress, and if it exceeds 30%, it is judged that the thickness cannot be changed while the rolling is in progress. As a result, for the above combination of the preceding material and the following material, the gap opening plate was conventionally performed 20 times per month, but the gap opening plate was reduced to 15 times by the embodiment. This improved the operating rate of the tandem rolling mill.

[0097] Although the embodiments of the present invention have been described above, the present invention is not limited by the descriptions and drawings that form part of the disclosure of the present invention according to the present embodiments. In other words, other embodiments, examples, and operation techniques, etc., made by those skilled in the art based on the present embodiments are all included in the scope of the present invention. [Explanation of symbols]

[0098] 1. Continuous cold rolling equipment 2 Tandem rolling mill 3. Rolling controller 4. Control computer 5 Rolled material 21 Work roll 22 Roll peripheral speed control device 23 Rolling control device 24 Rolling load detector 25 Roll position detector 26 Tension meter 27 Thickness gauge W Junction

Claims

1. A method for determining whether or not a running thickness change is possible when a rolling target material in which a preceding material and a succeeding material are joined via a joint is continuously rolled by a tandem rolling mill, comprising: A setting value acquisition step of acquiring a set value of the roll gap and the roll peripheral speed of the rolling stand for a preceding material before starting to change the set values ​​of the roll gap and the roll peripheral speed in at least one rolling stand of the tandem rolling mill; a tension fluctuation calculation step of calculating a tension fluctuation when the joint passes through the rolling stand while maintaining the set values ​​of the roll gap and the roll peripheral speed for the preceding material; A determination step of determining whether or not the running thickness can be changed based on the tension fluctuation amount calculated in the tension fluctuation amount calculation step; A method for determining whether or not a running thickness change is possible, including:

2. 2. The method for determining whether or not a running thickness can be changed according to claim 1, wherein the tension fluctuation calculation step calculates a tension fluctuation amount when the joint passes through the rolling stand while maintaining the set values ​​of the roll gap and roll circumferential speed for the preceding material, using the set values ​​of the roll gap and roll circumferential speed of the rolling stand for the preceding material acquired in the set value acquisition step, and the thickness and deformation resistance set for the succeeding material passing through the rolling stand.

3. 2. The method for determining whether or not a flying thickness change is possible according to claim 1, wherein, in the flying thickness change, a start point of the change in the roll gap and the roll peripheral speed is set to a position of a preceding material, and an end point of the change in the roll gap and the roll peripheral speed is set to a position of a following material.

4. 2. The method for determining whether or not a running thickness change is possible according to claim 1, wherein a difference between the deformation resistance of the preceding material and the deformation resistance of the following material is 80 MPa or more.

5. A method for changing a flying thickness, comprising: using the method for determining whether or not a flying thickness change is possible according to any one of claims 1 to 4; executing a flying thickness change when it is determined that a flying thickness change is possible in all rolling stands of the tandem rolling mill; and changing the set values ​​of the roll gap and roll peripheral speed of the rolling stand for the following material when it is determined that a flying thickness change is not possible in at least one rolling stand of the tandem rolling mill.

6. A device for determining whether or not a running thickness change is possible when a rolling target material in which a preceding material and a succeeding material are joined via a joint is continuously rolled by a tandem rolling mill, comprising: A set value acquisition means for acquiring the set values ​​of the roll gap and the roll peripheral speed of the rolling stand for the preceding material before starting to change the set values ​​of the roll gap and the roll peripheral speed in at least one rolling stand of the tandem rolling mill; a tension fluctuation calculation means for calculating a tension fluctuation when the joint passes through the rolling stand while maintaining the set values ​​of the roll gap and the roll peripheral speed for the preceding material; A determination means for determining whether or not the running thickness can be changed based on the tension fluctuation amount calculated by the tension fluctuation amount calculation means; A device for determining whether or not a running plate thickness can be changed.

7. A program for determining whether or not a running thickness change is possible when a rolling target material in which a preceding material and a succeeding material are joined via a joining portion is continuously rolled by a tandem rolling mill, the program comprising: Computer, A set value acquisition means for acquiring the set values ​​of the roll gap and the roll peripheral speed of the rolling stand for the preceding material before starting to change the set values ​​of the roll gap and the roll peripheral speed in at least one rolling stand of the tandem rolling mill; a tension fluctuation calculation means for calculating a tension fluctuation when the joint passes through the rolling stand while maintaining the set values ​​of the roll gap and the roll peripheral speed for the preceding material; A determination means for determining whether or not the running thickness can be changed based on the tension fluctuation amount calculated by the tension fluctuation amount calculation means; This is a program that determines whether or not the thickness can be changed while the ship is in flight.

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